1. Field of the Invention
This invention relates generally to inflatable-type modular occupant restraint systems for passenger vehicles or, as they are more commonly known, air bag restraint systems. More particularly, this invention relates to an air bag module subassembly which can be attached to an instrument panel substrate of a vehicle to form a complete air bag restraint system.
2. Description of Related Art
An air bag restraint system typically includes a canister, which has an open side and which canister encloses an inflator and at least part of an air bag, and a cover which conceals the module from view. A driver side air bag module is typically mounted in the center of the steering wheel behind a protective cover. When the air bag module is designed for the passenger side of a vehicle, the container may be located just behind the vehicle dashboard, cosmetic cover, or passenger side instrument panel (hereinafter referred to as "dashboard") and the cover may form an integral part of the vehicle dashboard.
When the vehicle is involved in a collision, a crash signal initiates operation of the inflator to cause the air bag to deploy. The inflator provides an inert gas (e.g., nitrogen) which is directed under pressure into the air bag to force the air bag out of the canister incorporated in the module and into the passenger compartment of the vehicle. As the air bag is forced out of the module, the pressure exerted on the driver-side protective cover or dashboard causes selected portions of the cosmetic cover to separate, in a predetermined manner, along tear seams or breakaway seams (hereinafter referred to as "tear seams") to enable the air bag to be directed into the passenger compartment.
Typically, an air bag inflator assembly as a complete unit is attached to the inside of a vehicle dashboard as is illustrated by Webber et al., U.S. Pat. No. 5,263,739, and Seki et al., U.S. Pat. No. 5,087,067. These air bag module assemblies include a canister containing an inflator and at least part of an air bag cushion. As the designs of automotive air bag restraint systems are reevaluated in order to reduce their size and complexity, it has been noted that the use of existing vehicle components as part of the air bag assembly would simplify the air bag restraint system. Therefore, it would be preferable to provide an air bag restraint system subassembly that works in conjunction with the existing motor vehicle hardware to produce the air bag restraint system. In these instances, it has been determined that it is preferable to have an air bag inflator assembly which can easily be attached to the dashboard substrate to form an air bag module assembly without the necessity for a separate air bag canister. "Substrate" herein means the structural components which support the dashboard.